Productivity, efficiency, and availability are the three factors that influence the amount of time you and your project management team need to complete a project task:

Productivity: The results you produce for each unit of time you spend working on the task. Your productivity on a task depends on the nature of the task and your ability to perform the required work.

Efficiency: The amount of time in your total work day that you spend on project tasks as opposed to nonproject activities, such as attending required company meetings, reading technical journals and articles, getting a drink of water, going to the restroom, and talking about non-work-related topics with coworkers.

If you spend every moment of your day on the job doing nothing else but working on project tasks, you’re being 100 percent efficient.

Availability: The amount of time you’re at work as opposed to out on leave. You determine your availability based on the number of paid-leave days your organization allows you to take, such as annual leave, sick leave, holidays, personal days, and maternity leave.

If your organization allows you to take a total of 39 days of leave during a 260-day period (1 year = 52 weeks x 5 days per week = 260 days), you would be available to work on assignments for your organization for 85 percent of the 260-day period.

As a project manager, you may need to assign tasks to different people on your team. In doing so, you have to consider how much time your team members will need to complete those tasks.

Assigning someone a reasonable amount of time to complete a task requires that you take into account not just what a person can accomplish when she’s working on the task but also the reality that even if you assign her to work full time for a period of time, she won’t be able to devote 100 percent of that time to task work.

Consider the following real-life example:

A man who attended a project planning training session was convinced that he took efficiency into account when he estimated needed levels of resources for his projects. His organization had recently performed an internal study and determined that each year, a typical employee spent about 25 percent of his or her time on sick leave, holiday leave, vacation leave, personal leave, and administrative leave.

As a result, he defined full-time availability to be 120 person-hours each month — 75 percent of the approximately 160 person-hours an employee was potentially available to work during a month. (He derived his estimate of 160 person-hours potentially available by multiplying 8 hours per day by five days a week by four weeks per month.)

The training session leader explained to him that the 120 person-hours estimate he derived was the total time an employee was available each month and, unfortunately, that people didn’t work at 100 percent efficiency for all the hours they were available.

To be accurate, he needed to consider that a person had about 90 productive hours each month to spend on project work — if he considered that the person worked at 75 percent efficiency. (You get 90 person-hours by multiplying the 160 hours potentially available by the 75 percent availability factor and then multiplying that number by the 75 percent efficiency factor.)

His reaction to the trainer’s suggestion was interesting: He completely rejected the analysis! He said that he refused to tell the people on his project that they had to do only six hours of work for every eight hours they charged to his project. He didn’t realize that they were doing this already.

He could recognize it and reflect it in his plans or he could ignore it, but ignoring it wouldn’t change the reality that it was occurring.